Patent GB-477782-A (GB)
Title: Improvements in or relating to pattern controlled milling machines
IPC: B23Q35/18
Filed: 1936-07-10
Abstract: 477,782. Milling-machines. CINCINNATI MILLING MACHINE CO. July 10, 1936, No. 19206. Convention date, July 10, 1935. [Class 83 (iii)] [Also in Group XXIX] In a pattern-controlled milling-machine the work and pattern are rotatably mounted on a support movable longitudinally and a cutter and tracer are movable towards and from the work and pattern, all the movements being hydraulically operated under control of the tracer. The machine comprises a base 10 having vertical guides on which a knee 12 is movable. A saddle 14 is movable on horizontal guides 13 on the knee and carries a horizontally movable table 16 which may he provided with a headstock 152 and tailstock 153 for rotatably supporting a work piece 144 and a pattern 143. Further vertical guides on the base carry a slide 18 which supports the rotary tool-spindle 19 and the tracerhead 141. Driving machine-spindle.-An electric motor 21, Fig. 2 on the base is connected by a chain 23 to a shaft 25 which may be coupled by a friction clutch 26 to a shaft 31. The latter drives a shaft 28 in either direction at one of sixteen different speeds through a change speed gear including slidable gear pairs 32, 33, 44, 55 and an idle-gear reversing train 51,52, the shaft 28 being connected to a bevel gear 30 splined on the cutter spindle 19. Work-table feeds.-The work and pattern table 16 is traversed parallel to the work axis either at a rapid traverse rate or at a slow feed rate by means of a screw 98, Fig. 2, co-operating with a nut on the saddle 14, A gear 62 on the motor driven shaft 25 rotates a shaft 60 which drives a shaft 82 either through a variable feed-drive including sliding gear pairs 69, 78 and gear 81 or through a rapid traverse train 64 and gear 65, a clutch 83 connecting one of the gears 65, 81 to the shaft 82. A vertical splined shaft 85 connects shaft 82 to a gear 86 on the knee 12 and this drives a splined shaft 91 on the knee through gears 90. A bevel gear 92 on the saddle 14 is driven by the shaft 91 and drives a bevel reversing gear 97 which rotates the screw 98 through a clutch 93. The saddle 14 is fed by screw means rotated from a gear 107 connected to the gear 90 by an idle-gear reversing train 104, 105 controlled by a hand-operated clutch 108, and the knee 12 is fed by a feed screw driven by a shaft 111 rotated through an idle-gear reversing train 109, 110 controlled by a hand-operated, clutch. 112. The clutch. 93 for controlling the table 16 may be operated by hand or by dogs 116, 1.17, Fig. 1, on the table engaging the clutch lever 115 to disengage the feed at the end of a traverse. The clutch 83 is controlled by a handle 133, Fig. 1, through rack and pinion mechanism 124, 127, 130, Fig. 2, and a yoke 121, a spring 123. being provided for engaging the feed gear 81 in the normal position. The main clutch 26 is controlled by a hand lever 134. Copying.-The pattern 143 and work 144 are given a spiral movement relatively to the tracer. 170 and cutter 20 by means of a hydraulic motor 145, Fig. 2, which drives the work arbor 149 through worm gearing 148. A gear 154 on the arbor rotates the feed screw 98, to move the work axially, through change speed gearing 165 and a movable gear 162 controlled by hand to disengage the drive when it is desired to return the table 16 by means of the rapid traverse. Axial or universal movement imparted by the pattern to the tracer displaces a servo valve 200 controlling flow of fluid to a hydraulic cylinder 171 whose piston 172 is connected to the slide 18. Fluid is led above and below the piston by passages in the rod 174 and pipes 177, 178 communicating below and above the neutral position of valve 200. The valve 200 is supplied with fluid from a variable delivery pump 184 by pipe 183. A spring 189 tends to move the pendulum 188 of the pump to maximum delivery position, but when the outlet is stopped by the valve 200, pressure leading to a cylinder 191 reduces the output of the pump, the spring being adjusted to maintain a predetermined pressure in the pipe 183. When the tracer is in contact with the pattern the valve 200 is in its central neutral position and no fluid passes to the pipes 177, 178 but protuberances or hollows on the pattern displace the valve from this position and connect one end of cylinder 171 to the pressure supply and. the other end to the exhaust line 203. The motor 145 is supplied with fluid by a separate non-reversible variable delivery pump 204 whose outlet 205 leads to a reversing valve 215 through pipe 207 and a check valve 210 which maintains a predetermined pressure in the pipes 207, 211. The reversing valve which is controlled by a hand lever 223, admits fluid to one end or the other of the motor 145 through pipes 218, 219 the exhaust from the motor being returned to the pump by a pipe 222 so as to form a closed circuit. When the cylinder 171 is actuated to feed the cutter up or down the valve 200 connects the pipe 211 to exhaust, thereby lowering the pressure in pipe 207 and allowing the valve 210 to throttle the supply from the pump to the motor 145, so as to slow down the rotation of the work and preserve a constant cutting speed, whilst if the tracer encounters an abrupt shoulder on the pattern the rotation of the work is stopped completely until the shoulder has been surmounted. The valve 200 also connects pipes 211, 229, when displaced, to byepasa part of the output from the pump to the inlet and so reduce the supply to the motor 145 to decrease its speed. A spring 232 tends to move the pendulum 233 of the pump 204 to decrease the delivery of the pump but is prevented from acting fully by a cam 234 attached to the tracer-head 141 on the slide 18 so as to move therewith. The cam is tapered lougitudinally so that as the cutter is moved upwards to operate on work of larger diameter the speed of rotation thereof wll be reduced in order to preserve a constant surface cutting speed. The circumferential shape of the cam is eccentric so that the rotational speed of the work may be varied by rotating the cam through a handle 239, a scale and pointer 240 being provided to indicate the setting. On completion of a copying operation the tracer may be lifted by a hand crank 246 engaging a flange 250 thereon, thereby raising the slide 18 and simultaneously stopping rotation of the work. The gear 162 may then be disengaged and the table 16 returned by the rapid traverse mechanism. A handoperated relief valve 251 is provided to shortcircuit the motor 145 when it is desired to stop rotation of the work independently of the position of the tracer, and a spring-relief valve 253 operates automatically in a similar manner if the pressure in pipe 207 should rise unduly. A switch 260 in the electric mains 260<1> for the main motor 21 is closed by pressure from the pump 184 so as to ensure that a motor 262, Fig. 1, which drives the pumps 184, 204, sliall be started before the motor 21 can be started. The work may be rotated and moved axially by hand through a hand wheel 263 on the worm shaft 147, and a friction clutch 158 is incorporated in the drive to the screw 98 to prevent damage if the clutch 93 should be engaged whilst the motor 145 is operating. The cutter spindle may be adjusted axially on the slide 18 by means of a rack and pinion 267 and hand wheel 268.